Imaging apparatus are primarily provided in two different configurations—liquid ink imaging apparatus and dry toner imaging apparatus. As used herein, “imaging apparatus” includes any type of apparatus which is configured to generate an image on a sheet of imaging media (such as paper or the like), and includes printers, photocopies, facsimile machines, and combinations thereof (i.e., so-called “multi-function printers”). Liquid ink imaging apparatus are commonly known as “ink-jet imaging apparatus” because tiny droplets of liquid ink are projected from a print head onto a sheet of imaging media to form an image. Liquid ink is provided to ink-jet imaging apparatus by an ink delivery system, which is typically either a single-use replaceable cartridge or a tank resident within the imaging apparatus and which is refilled periodically from a larger reservoir.
Regardless of which type of ink delivery system is used, one of the main goals is to reduce (and preferably eliminate) extraneous ink from dripping or “drooling” out of the print head. Two primary designs are used to achieve this objective. The first design is to use a capillary foam to entrain the liquid ink, wherein the capillary action of the foam is sufficient to overcome gravitational forces which would otherwise tend to cause the ink to drip or drool from the pint head. The second design is to use a negative pressure system to impart a slight negative pressure (i.e., a pressure slightly lower than ambient atmospheric pressure) on the liquid ink, thereby biasing ink flow into the reservoir until acted on by the print head, thus forcing the ink out of the reservoir. Another primary objective in ink delivery systems is to reduce (and preferably, eliminate) any entrained air from entering the liquid ink, which can adversely affect performance of the imaging apparatus and the resultant image quality. One of the more common types of negative pressure system utilizes an expansible bag or bladder which is placed within the ink reservoir. Such a system is depicted in FIG. 1 (described below). These prior art bladders typically include a separate metal spring, generally in the shape of a shaped plate, which facilitates in biasing wall members of the bladder either towards or away from one another.
The prior art designs are generally effective in reducing or eliminating ink drool from the print head of an ink cartridge. However, the metal spring members which are used to bias the bladder walls to predetermined positions relative to one another can sometimes puncture the bladder during assembly, rendering the cartridge useless. Further, a separate spring member adds to the complexity of the design and the construction of the bladder system.
What is needed then is a liquid ink containment and delivery system for use in liquid ink imaging apparatus which achieves the benefits to be derived from similar prior art devices, but which avoids the shortcomings and detriments individually associated therewith.